In a small bowl, toss the onion with the lime juice. Let stand for 40 minutes. Working with 1 mango at a time, score the skin into quarters. Peel half the mango and cut 1/4-inch lengthwise slices down to the pit. Cut crosswise to release the slices. Repeat with the other side. In a large bowl, combine 2 cups of water with the salt. Add the mangoes and let stand for 40 minutes. Drain the mangoes and pat dry. Transfer to a large bowl and add the orange juice. Drain the onion and sprinkle over the mangoes with the chopped chiles. Garnish with the coriander. Serves 4.